THIS INVENTION relates to a force amplifying initiating device for a cartridge. It relates also to a cartridge including a force amplifying initiating device.
A force amplifying initiating device of the kind to which this invention relates, includes a body having first and second open ends and a firing pin arrangement held within the body such as to be operatively exposed to its surroundings via the first open end. The body is, in use, located to a cartridge shell such that the firing pin is operatively aligned with a primer of the cartridge via the second open end. In use, when the cartridge is to be fired, the first open end of the force amplifying initiating device is subjected to a pressure pulse or shock wave which actuates the firing pin to initiate the primer.
For purposes of this invention, a force actuating initiating device as described will be referred to as an initiating device.
The Applicant believes that an initiating device in accordance with this invention will advantageously be usable for firing a cartridge placed in a remote location or a location which is difficult to obtain access to. For example, in the breaking of rock and the like, it is known to place a rock breaking cartridge in a hole drilled into the rock, and to fire the cartridge. Advantageously, the hole may be filled with a medium, such as water, a gel, or the like, which propagates pressure pulses or shock waves well. This is referred to in the field of rock breaking as a xe2x80x9cdown the holexe2x80x9d cartridge or xe2x80x9cdown the holexe2x80x9d rock breaking. Although this invention is not limited to xe2x80x9cdown the holexe2x80x9d applications, it is expected to be used extensively in such applications.
In accordance with a first aspect of this invention, there is provided a force amplifying initiating device suitable for use to initiate a primer of a cartridge in response to a pressure pulse or shock wave, the initiating device comprising
an open ended body having a fore opening and a rear opening and a locating formation for locating the body to a cartridge in a predetermined relation to a primer of the cartridge;
a firing pin having a fore operative end and a rear end, and being movably contained in the body such that said fore operative end is in alignment with the primer via said fore opening of the body and such that said rear end is exposed via said rear opening of the body, in which said fore operative end is appropriate to initiate a rim fire primer having an initiating rim of predetermined effective diameter, said fore operative end tapering from a rear base to a fore point, the rear base having a transverse dimension at least commensurate with the effective diameter of the initiating rim of the primer and the fore point having a transverse dimension smaller than the effective diameter of the initiating rim of the primer.
The fore operative end of the firing pin may be round, said transverse dimension of the base being the diameter of the base, and the transverse dimension of the point being the diameter of the point.
The fore operative end of the firing pin may be generally conical, the point being rounded.
An included angle of the generally conical fore operative end may be between 160xc2x0 and 40xc2x0, preferably between 100xc2x0 and 60xc2x0, most preferably about 70xc2x0.
In accordance with a second aspect of this invention, there is provided a combination of a force amplifying initiating device as herein described and a primer for a cartridge, which primer is a rim fire primer having an initiating rim of predetermined effective diameter.
In accordance with a third aspect of this invention, there is provided a pressure generating cartridge assembly including a pressure generating cartridge having a rim fire primer having an initiating rim of predetermined effective diameter, and a force amplifying initiating device as herein described, in which the force amplifying initiating device is located to a body of the pressure generating cartridge.
Said primer may be mounted in said fore opening of the body of the initiating device and said initiating device may be located within a body of the cartridge at a rear end of the cartridge.
By way of development, said fore opening of the body of the initiating device may be in the form of a collar within which the primer is embraced.
Said fore point of the firing pin may be in alignment with a central portion of the rim fire primer within said initiating rim.
The initiating device may be formed of an assembly of synthetic polymeric mouldings.